NEW YORK, NY, USA - For the second time this year, No.13 seed Belinda Bencic has ended a Naomi Osaka title defence in the fourth round, today beating the No.1 seed 7-5, 6-4 in one hour and 26 minutes at the US Open.

The Swiss player's first of three wins over Osaka this season came at the same stage of Indian Wells in March 6-3, 6-1 - one of a Tour-leading seven Top 5 victories that she has scored in 2019 - and in one of the most eagerly anticipated last-16 clashes between two leading members of Generation 1997, reprised the result in a more tightly contested high-quality affair.

Bencic's prior wins had helped her concentrate on what she needed to do, she said afterwards. "I just came with the same mentality like I played her before," she explained. "[I] just really focused on the game and not about the hype or the occasion, the stadium and the round. After the match, it feels definitely different. It feels like this was the most important one."

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Bencic, who described her point construction and shot selection as "very much on instinct", said adaptation and anticipation had been key. "Obviously I always adapt to my opponent - that's just how I play," she said. "I don't have the biggest power, don't have the most winners or most aces. But I think I can really read the opponent's game well. I definitely try to do that against anyone, not only against her. Just taking the ball early and anticipating her... I think my game probably matches up well against hers."

Osaka agreed, saying: "She played pretty clean. I think she had a specific plan she wanted to execute."

The result moves the former World No.7, who won all nine of her net approaches today, into her first Grand Slam quarterfinal since making the last eight here on her 2014 debut - and also means that Osaka will lose the World No.1 ranking after the tournament to Roland Garros champion Ashleigh Barty.

The 21-year-old was sad but sanguine afterwards, though. "Right now I have this feeling of sadness, but I also feel like I have learned so much during this tournament," Osaka explained. "Of course I wanted to defend this tournament. [But] I feel like the steps that I have taken as a person have been much greater than I would imagine at this point. So I hope that I can keep growing. I know that if I keep working hard, then of course I'll have better results."

A positive for Osaka was that she felt she improved her game over the summer. "I don't feel like I put so much weight on one single match," she explained. "As a whole I want to see that I played better matches through the summer. Because I feel like definitely the tournament that I played here has been the best one so far."

Bencic got off to the faster start, dominating with the early strike, depth and easy redirection on her backhand wing, and as she held four points to move up a 3-0 double break, the match briefly seemed as though it could be one-way traffic.

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But having coughed up a pair of early double faults already, Osaka gathered herself, finding fine first serves to save all four and overpowering Bencic with her forehand to break back for 2-2. This set the stage for a cleanly played opener in which there was nothing between the two competitors until its closing stages. Both ended it with positive ratios of winners to unforced errors - 16 to 11 for Osaka and 15 to eight for Bencic - and only one further game would feature a break point.

That was the 10th game: set up beautifully by Bencic by effortlessly redirecting her forehand around the court, the 22-year-old took it with a backhand pass before, sweeping through two more magnificent backhand winners, she overcame two double faults to seal the first set.

The Dubai champion continued to put on a show in the second set, striking on the Osaka serve in the fifth game with two moments of magic: a lightning flash of a forehand return followed by a cheeky angled smash reminiscent of Hsieh Su-Wei, and an outstanding backhand pass struck off a full-power Osaka drive volley that had the crowd roaring. The Japanese player responded with her third double fault of the day for a break that would prove decisive.

Although the statistics on paper would indicate a stronger serving performance by Osaka, who boomed down 10 aces to Bencic's none and committed only three double faults to Bencic's six, it was in fact the World No.12 - who hit 14 winners to a meagre four unforced errors in the second set - whose delivery was impregnable.

Bencic conceded only four points on serve in the second set, sealing victory with a one-two punch to set up a quarterfinal against either No.23 seed Donna Vekic or No.26 seed Julia Goerges - and guaranteeing that the US Open will see a brand new Grand Slam finalist emerging from the top half of the draw.